STEPPED PISTON FOR BALANCED PILOT OPERATED SAFETY RELIEF VALVE

摘要

In a pressure relief valve comprising a stepped piston (36) with a reduced-area end portion (A4) and an enlarged-area end portion (A5), pressure from the main line (32) is directed into a chamber (42) to act on the enlarged area of the piston to force the reduced-area end into sealing contact with a valve seat (38). The enlarged area end portion of the piston (36) is sealed against back pressure in the exhaust line (34). As shown when mainline pressure P4 exceeds a predetermined limit, a pilot valve (40) opens to vent chamber (42) and allow mainline pressure to force piston (36) from its seat. IMAGE